Apparatus and method for accurate and precise positioning of cellular antennas

ABSTRACT

An antenna mounting apparatus ( 10 ) in which an antenna bracket ( 32 ) can be rotated relative to a mount ( 20 ) in an azimuth direction and is selectively, automatically locked in position.

The present invention is concerned with an apparatus and method for theaccurate and precise positioning of antennas. More specifically, thepresent invention is concerned with an apparatus and method whichfacilitates accurate and precise positioning of cellular antennas tospecifications set by a network operator.

Cellular antenna structures are used by cellular communications networksand service providers to mount antenna systems at a desired height fromthe ground for uninterrupted transmission and reception of cellularradio signals between the antenna system and a mobile device operated bya user.

A typical antenna base station structure is shown in FIG. 1, andcomprises a tower or pole 1 and one or more axially spaced antennasupport brackets 2 attached to the tower or pole 1. Attached to thebrackets 2 and parallel to the pole 1 there is provided an antennasupport 3, which is elongate and tubular. A hinged tilt bracket 4 and ajoint 5 are attached to the antenna support 3 in axially spacedpositions and an antenna 6 attached thereto. The length of the poletherefore determines the height of the antenna 6 from the ground. RFcables 7 are attached to the antenna 6.

Usually, the tower is firstly assembled at the location of installationand then the support brackets are mounted to the tower. The antennas areattached to the support brackets by means of mounting bolts and screwsor other securing means, and are manually adjustable in three dimensions(heading (also known as azimuth), tilt and roll).

In order to facilitate this adjustment, the tilt bracket 4 isarticulated to allow the top of the antenna 6 to move away from thesupport 3, and thereby rotate the antenna about the joint 5 (which has ahorizontal axis of articulation) to adjust the antenna down-tilt angle.In the event that up-tilt is required then the tilt bracket 4 and thejoint 5 can be swapped. The antenna heading (rotation about a verticalaxis) can be adjusted by loosening the attachment of the bracket 4 andjoint 5 to the support 3 and manually rotating the antenna 6 about thesupport 3. The antenna roll angle is usually set at zero and typicallynot adjustable.

The base station shown in FIG. 1 has a single sector (i.e. a singleangular region covered by the direction antenna 6), but usually threeregions (i.e. three antennas) are provided, each covering 120 degreearcs.

A typical cellular communications antenna is directional, comprising anelongate, planar metal reflector and a series of dipoles positioned in aline along the surface of the reflector. Usually, a cover is used tocover the dipoles in order to environmentally protect them. The cover isconfigured to be as transparent to electromagnetic radiation as possiblein the cellular communications frequency range in order not to affectthe antenna radio propagation characteristics. Cover materials having asubstantial plastics material component such as GRP or ASA are commonlyused.

As cellular networks are deploying broadband technologies for higherdata rates (e.g. 3G/4G) the positioning of cellular antennas in a globalsense is increasingly important. This is particularly true sincebroadband technologies are interference limited technologies. This meansthat higher the signal to interference ratio (C/I), the lower are themaximum data rates that can be achieved. The finite transmitted powerfrom an antenna needs to be accurately directed to the planned targetarea in order to keep the signal to interference ratio under control.Accurate positioning of antennas reduces unwanted interference betweenadjacent sectors while directing the maximum signal power where isneeded thus achieving minimum signal to interference ratio both insideand outside the target sector.

Capacity oriented network architectures should deploy antennas that canbe dynamically adjustable such that their radiation pattern can redirectthe finite network bandwidth from one area to another. More advancedantennas are remotely adjustable via electrical motors (or other means)such that their azimuth and tilt angles can be adjusted in order toprovide the best possible coverage. For example if a large number ofusers are in a certain area then a group of antennas can be realignedsuch that their respective coverage offers the required capacity forthat area. As such, it is very important that the absolute direction ofthe antenna is known, so that its position can be accurately adjusted.

Desired antenna position is usually determined through a radio planningprocess, carried out by the network operator. This process providesdetails of the desired global position of the antenna, as well asspecific values of heading, tilt and roll.

To achieve high network performance, provide high quality radio linktransmissions and reception and ensure high spectrum efficiency,directional antennas must be aligned with minimum inaccuracy (less than±1°) in the degrees of freedom (heading, tilt and roll). Accuratealignment of directional antennas is of paramount importance in acompetitive wireless communication industry, as even small errors inazimuth and tilt alignment (more than ±5° for azimuth and more than ±1°for tilt) can seriously degrade radio network quality.

Several prior art solutions are currently available for antennaalignment purposes. For example, US20090021447 and US20110225804 eachdescribe devices for measuring the orientation of an antenna in threedegrees of freedom, i.e. heading, tilt and roll. The devices aredirectly secured to an antenna by a technician, rigger or climber anddisplay the measurements performed in real time allowing the user toaccurately align an antenna to the desired directions.

One deficiency of these prior art devices is that they need to beoperated by a technician, rigger or climber at the location of theantenna. As a result, the use of the measurement devices described inUS20090021447 and US20110225804 always need to be operated by a user inreal time. Every time the antenna needs to be adjusted, the technician,rigger or climber needs to scale the tower, mount the system to theantenna and carry out the required adjustment.

Such devices are also very expensive (many thousands of Euros), and assuch cannot be permanently mounted on antennas as this wouldsignificantly increase unit cost, and therefore the capital expenditure(CAPEX) of the operator.

Measurement uncertainty is the sum of systematic and randomuncertainties introduced in the measurement process. Systematicuncertainties are introduced from a measurement device while randomuncertainties are introduced from the method followed by operating themeasurement device and collecting and interpreting the measurementresults (i.e. human error in use of the device). The measurement devicesdescribed in US20090021447 and US20110225804 cannot exclude the humanerror introduced in the measurement process because they need to beoperated at the antenna location by a technician, rigger or climber. Thealso need to be affixed to the antenna in the correct manner each timeadjustment is required. This is generally undesirable.

Furthermore, due to the modern networks' dynamic nature, repeatableantenna azimuth and tilt re-adjustment during the lifecycle of a basestation site (for one or more antenna systems) is required; therefore,the antenna brackets, the antennas or the antenna structure itselfshould be capable of facilitating such needs. Antenna azimuth and tiltreadjustment has to be performed with the same high degree of accuracyas the original installation.

Antenna azimuth and tilt re-adjustment should ideally take place withoutthe need to climb on the tower top and manually adjust the antennaposition. Manual reposition involves high operational expenditure (OPEX)due to climbing, as well as health and safety risks for antennatechnicians, riggers and climbers. It is also desirable to reduce humanexposure to the strong electromagnetic fields proximate the antennas. Atpresent, most network operators inhibit antenna operation during thetime that such works are performed on the antenna system, thuspreventing coverage from the selected antenna and/or base station. Thisis also undesirable.

As discussed, the devices disclosed in US20090021447 and US20110225804do not disclose remote (only local) re-adjustment of the antennaorientation. However, should remote re-adjustment be used, thisrequirement cannot be satisfied by this prior art.

A prior art antenna that offers built-in remote azimuth and tiltadjustment by electromechanical actuation and provide heading, tilt androll measurement means is disclosed on US20090195467. A problem withthis prior art is that the adjustment mechanism is integrated with theantenna itself. This forces the operator to adopt one type of antenna,and also forces them to invest in a new antenna. Preferably, theoperator should be able to select the appropriate antenna for its radiocharacteristics in the first instance.

A further problem encountered by modern cellular antennas is in the useof the MIMO (multiple input multiple output) protocol. This type ofsmart antenna technology currently uses arrays of cross polarizeddipoles to form multiple antennas under the same housing (radome) inorder to increase data bandwidth performance due to better exploitationof both transmit and receive de-correlated RF paths (polarizationdiversity transmission and reception). Such antennas, although offeringhigh spectrum efficiency, are difficult to install on the antennastructure due to their physical dimensions, complexity of installationand aesthetics. Furthermore, antennas supporting MIMO technology forvarious configurations (i.e. 2×2, 4×4, etc) are significantly moreexpensive than the legacy cross polarized antennas used today.

Another disadvantage of the prior art MIMO antenna technology is thatdue to their size, steering capability of the antenna radiation patterncannot be easily achieved with electromechanical actuation. This resultsin an inherent limitation of the antenna technology as it cannot satisfythe modern networks' dynamic needs, where repeatable antenna azimuth andtilt re-adjustment during the lifecycle of a base station site (for oneor more antenna systems) is required.

Alternative use of the MIMO technique deployment requires thede-correlation to be achieved by spacing dipoles apart (horizontally orvertically, by a specified distance in wavelengths (λ)—distance dependson both MIMO performance requirements as well as other parameters suchas RAN technology used and modulation/coding schemes) in order toachieve increased data bandwidth performance due to better exploitationof both transmit and receive de-correlated RF paths (space diversitytransmission and reception). In order to manage best possible decorrelation effects by spacing, two or more antennas need to be spacedapart in such a way that two antennas should point in exactly the same 3dimensional direction having known distance in wavelengths (λ) to eachother. This is required for the de-correlation to take maximum effectper performance targets and technology deployed

MIMO technique deployment by spacing dipoles (or antennas) apart withhigh precision mapping in three degrees of freedom (heading, tilt androll) for two antennas at a distance apart can be challenging forantenna technicians, riggers or climbers (for the reasons discussedabove). Furthermore, accurate fixation of two antennas at a specifiedhorizontal or vertical distance in wavelengths (λ) whilst also achievingprecise parallelism and/or verticality to each other is alsochallenging. The aforementioned installation problems, when attemptinghigh precision positioning and alignment of two or more antennas forMIMO technique deployment by spacing, is generally difficult (if notimpossible) to handle with today's installation practice and tools.

A further problem with directing antennas in the desired direction, inparticular by remote actuation, is “play”, or free movement, in theactuation system. The use of electric motors and gear trains results insome inevitable backlash which can cause the antenna to move in use. Inparticular worm gears (which offer an advantage in gearing) havetypically high backlash.

A problem with existing antenna installations is the fact that they aregenerally exposed to the external environment, i.e, repeated cyclicalwind loading on the antenna. The repeated buffeting of the antenna overtime may cause wear in the antenna mounting components, in particular ifa remotely driven antenna is provided. Therefore the life cycle of thesecomponents is limited. One solution is to cover the entire assembly witha radome, however this restricts the space available requiring anyadjustment mechanism to be integrated with the antenna itself.

GB2251521A discloses an orientation adjusting device for an antennawhich uses a worm gear. A problem with such arrangements is thatbacklash can be a problem, and complex mechanical modifications to thedrive train (such as that disclosed in the document) are required toalleviate backlash, adding cost and complexity to the assembly. Also,wind loading on the antenna acts to repeatedly and/or continuously backdrive the drive mechanism imposing the risk of failure over time.Although worm gears cannot be back driven, the gears have to be overengineered to cope with the induced stresses from e.g. wind loading, andin the case of backlash the potential repeated, small movements (whichmay cause fatigue). In the case of a gearbox, this means that the gearsbecome significantly larger and heavier than they would otherwise needto be.

A still further problem with remote actuation of antennas is that theelectrical specifications defined by industry standards set maximumcurrents for the operations to be performed on the antenna andassociated devices. This limits the size of the motor to be used forhigh torque applications, and necessitates a gearbox so that a smaller,lower current motor can be used, which in turn introduces further costand complexity into the system. As such, in a case that a remoteactuation system needs to be compliant to the industry standards, theproper balance between the motor and the gearbox size need to beaccounted in order to satisfy the application.

DE9010416U1 discloses an antenna mounting apparatus which is configuredto adjust the tilt angle of the antenna using a number of holes at thetop bracket to manually secure the antenna in position.

EP1753075A1 discloses an antenna mast in which the azimuth of eachantenna can be altered by manual rotation about a pivot point. Theantenna may be secured in position by aligning a hole on the antennabracket with one of several holes on the mast, and the user passing abolt (secured by a nut) through the aligned holes to secure the antenna.A problem with this invention is that positive user intervention isrequired to secure the antenna in place. As such, user error can resultin an unsecured antenna.

WO 00/46872 also uses a bolt with an array of holes to manually positionand lock the azimuth of the antenna.

It is an object of the present invention to provide an improvedapparatus and method for accurately mounting and adjusting the positionof cellular antennas whilst overcoming, or at least alleviating, theabove-referenced problems.

In accordance with a first aspect of the invention, there is provided amethod of modifying an existing cellular antenna base station,comprising the steps of:

-   -   providing an existing cellular antenna base station comprising a        mast;    -   attaching a reference frame to the mast;    -   providing a global orientation and position measurement device;    -   attaching the global orientation and position measurement device        to the reference frame;    -   measuring the global orientation and position of the reference        frame using the global orientation and position measurement        device;    -   removing the global orientation and position measurement device        from the reference frame;    -   providing an antenna mounting assembly having an antenna        bracket, the antenna mounting assembly configured to allow        movement of the antenna bracket relative to the reference frame,        the antenna mounting assembly comprising a sensor configured to        measure the relative movement of the antenna bracket to the        reference frame;    -   attaching an antenna to the antenna bracket.

The invention provides a significant advantage in the field of antennainstallation because it combines the ability to provide adjustableantenna orientation and position without requiring the constant orrepeated presence of an expensive global orientation and positionmeasurement device. Advantageously, once the position of the referenceframe has been determined, the antenna position can be adjusted, and theglobal orientation of the antenna (e.g. with respect to grid, magneticor true North) can be determined using a relative position sensor (e.g.an optical/magnetic rotary encoder or an electrical potentiometer) whichis inexpensive when compared to the global orientation and positionmeasurement device.

During the above method, the steps of attaching and removing themeasurement device are carried out with the reference frame in the sameposition—i.e. the reference frame does not need to be moved to aspecific position because the antenna mounting assembly provides therequired movement.

The method may comprise the steps of providing a further antenna andattaching the further antenna to the reference frame, for use in MIMOapplications. The antennas may be vertically or horizontally spaced inuse.

The existing cellular antenna base station may comprise a down- orup-tilt bracket attached to the mast, and the step of attaching thereference frame to the mast comprises the step of attaching thereference frame to the tilt bracket.

The antenna mounting assembly may comprise tilt and/or roll sensor todetermine the absolute tilt and roll of the reference frame which can beused in the calculations to position the antenna. Such tilt and rollsensors are also inexpensive compared to global orientation and positionmeasurement devices.

In many existing cellular antenna base stations, an antenna mount isattached to the tilt bracket, in which case the step of attaching thereference frame to the mast comprises the step of attaching thereference frame to the antenna mount. It is also feasible that theexisting cellular antenna base station comprises an antenna attached tothe mast—this antenna can be removed, the system according to theinvention installed, and the same antenna placed back on the basestation. A significant advantage of the present invention is themitigation of the need to purchase new antennas to achieve optimum andrepeatable alignment of the antenna.

Preferably the method comprises the steps of:

-   -   providing an azimuth steering assembly;    -   steering the antenna using the azimuth steering assembly;    -   determining the absolute heading of the antenna using the        measured position of the reference frame combined with data        provided by the sensor.

The same method may also apply for tilt and roll steering assemblies.

As mentioned above, the present invention allows for repositioning ofthe antenna without needing expensive, human operated global positioningsystems.

Preferably the method comprises the steps of:

-   -   providing an azimuth locking assembly;    -   locking the antenna bracket relative to the reference frame        using the locking assembly.

The same method may also apply for tilt and roll locking assemblies.

Advantageously this avoids the need for a large motor and/or gearbox toresist wind loading, and also avoids misalignments due to motor/gearboxbacklash.

According to a second aspect of the present invention there is providedan antenna mounting apparatus comprising:

-   -   a first mount,    -   an antenna mounting bracket attached to the first mount via a        first rotational joint to allow azimuth adjustment rotation        about a first axis;    -   the first rotational joint comprising: a first locking mechanism        arranged to lock the first rotational joint and a rotary sensor        arranged to determine the articulation of the first rotational        joint;    -   wherein the first rotational joint comprises an interface plate        defining: a drive interface for articulating the joint, a        locking interface for selectively locking the joint using the        first locking mechanism and a rotary sensor interface arranged        to provide an output reading from the rotary sensor.

The presence of an interface plate with steering, locking and a dataconnection allows the system to be an upgradeable “plug and play”system. The operator can select whether to provide a manual steering andlocking assembly for occasional antenna adjustment, or an automatedassembly for frequent, automated remote alignment.

The integral rotary sensor and data output means that a measurement toolis not required—thus reducing errors by manual adjustment. The climberor rigger can simply plug-in a diagnostic tool to read and display theantenna position calculated from the rotary sensor output.

The drive interface may comprise a spline, threaded shaft, flat shaft orthe like, capable of transmitting a torque. Preferably the rotationaldrive formation is a male or female formation for being received in, orfor receiving an actuator drive shaft in a mating arrangement.

Preferably each interface of the interface plate faces in a commondirection. More preferably the common direction is towards the ground inuse. This allows easier access for manual adjustment and/or replacementof the steering and locking mechanism.

Preferably the interface plate defines an actuator mounting formationfor attachment of an actuator housing to engage an actuator output shaftwith the drive interface in use.

Preferably the first rotational joint comprises a sealed housingcontaining the first locking mechanism and the rotary sensor. Preferablythe sealed housing is sealed to an IP rating, preferably at least IP67.This recognises the fact that the antenna is positioned outside, and maybe in a humid, icy, wet, dusty or dirty environment.

Preferably the locking mechanism comprises a first part coupled to thefirst mount, and a second part coupled to the antenna mounting bracket,which first and second parts comprise selectively alignable formationsarranged to be simultaneously engaged by a locking pin to secure thelocking mechanism. Preferably one of the first and second partscomprises a series of formations circumferentially spaced around thefirst axis at a first radius. Preferably the series of formations is aseries of locking bores.

A locking arrangement is then provided having an actuable locking pinarranged to move between an unlocked condition, and a locked conditionin which it simultaneously engages the first and second parts to lockthem together.

Advantageously the ability to lock the parts together aside from theinherent resistance of the motor means that the motor and/or gearboxdoes not have to react loads on the antenna all the time. In other wordsa load path between the components is formed separate from the motorshaft. This means that the motor and/or gearbox do not have to bedesigned to withstand back driving from e.g. wind loading, and thesystem is resistant to any motor backlash.

The locking pin may be linearly actuable. The locking pin may beresiliently biased to a locked condition. A resilient member may beprovided to bias the locking pin to the locked condition.

This type of sprung pin arrangement allows one handed operation of thelocking mechanism, as unlike the prior art the locking pin willautomatically engage. Further, and advantageously, the locking memberwill move to a failsafe locked position should an operator forget toensure that locking has occurred.

The locking arrangement may be manually actuated, or actuated by anelectric actuator.

A steering actuator may be provided having an electric actuator arrangedto provide a steering torque to the drive interface. A combined steeringand locking unit comprising the steering actuator and a lockingmechanism configured to engage the locking interface to lock the firstrotational joint may also be provided. Such a steering and locking unitshould preferably comprise an electrical connector to receive the outputreading from the rotary sensor.

There may also be provided a control system configured to:

-   -   receive an antenna movement command;    -   in response to the movement command;        -   disengage the locking mechanism,        -   move the mounting bracket with the first steering actuator,        -   determine the position of the antenna using the output            reading, and,        -   reengage the locking mechanism.

Preferably the assembly comprises a reference frame, in which the firstmount is attached to the reference frame. The exact global position andorientation of the reference frame is known, and as described belowmeasured to a high level of accuracy upon installation and subsequentmovement.

Preferably the reference frame is an extruded component. This provides aconstant profile for mating with adjacent components. It also allowsmounting at various positions along the length of the reference frame.

Preferably the reference frame is an extruded plate. The reference framemay also be an extruded pole.

Preferably the reference frame comprises a plurality of channelsarranged to receive a fastener of the first mount. Preferably thechannels extend along the length of the reference frame, and areconfigured to capture a fastener head.

It will be understood that the reference frame may be oriented with itsmain axis vertical or horizontal in use. In the latter case, two MIMOantennas can be mounted side-by-side and co-aligned to a high degree ofaccuracy.

According to a fourth aspect of the invention there is provided a methodof operating a cellular communications antenna comprising the steps of:

-   -   providing an antenna mounting system comprising: a mount; an        antenna mounting bracket attached to the first mount via a first        rotational joint to allow azimuth adjustment rotation about a        first axis; an electric motor arranged to drive the antenna in        rotation about the first axis; and, a locking mechanism arranged        to selectively lock relative rotation between the mount and the        antenna mounting bracket;    -   disengaging the locking mechanism;    -   engaging the electric motor to rotate the antenna mounting        bracket;    -   holding the antenna bracket in position using the electric        motor;    -   re-engaging the locking mechanism;    -   disengaging the electric motor.

Advantageously using the motor to hold the antenna mounting bracket inposition whilst the locking mechanism actuates keeps the componentsaligned in the correct position. For example, if the locking mechanismrequires a pin to be inserted into a bore, then alignment is paramount,and keeping the motor energised and able to hold the system in place isadvantageous.

Using such a locking mechanism also allows for a smaller motor to beused, because the motor is not constantly in use either holding theantenna mounting bracket in place or constantly correcting deviations inantenna position.

This invention alleviates the problem with e.g. wind loading trying toback drive the electric motor.

Preferably the method comprises the steps of:

-   -   providing a rotary movement sensor as part of the antenna        mounting system;    -   using the rotary movement sensor in conjunction with the        electric motor as part of a control system to hold the antenna        bracket in place during the holding step.

Preferably the antenna mounting system is an antenna mounting systemaccording to the second aspect.

According to a fourth aspect of the present invention there is alsoprovided an antenna mounting system comprising:

-   -   an antenna mounting apparatus according to the second aspect,        and,    -   a further antenna mounting apparatus having:        -   a further first mount, and,        -   a further antenna mounting bracket attached to the further            first mount via a further first rotational joint to allow            azimuth adjustment rotation about the first axis,    -   in which the antenna mounting apparatus and the further antenna        mounting apparatus are spaced apart in the direction of the        first axis.

Preferably the first mount is attached to a second mount via a secondrotational joint to allow azimuth adjustment rotation about a secondaxis, parallel to and offset from the first axis, such that the firstmount is an intermediate member between the second mount and the antennamounting bracket.

Preferably there is provided a second locking mechanism arranged toinhibit rotation of the first mount and the second mount, which secondlocking mechanism comprises a second locking pin arranged to selectivelyand simultaneously engage both the first mount and second mount.

According to a fifth aspect of the present invention there is alsoprovided an antenna mounting system comprising:

-   -   an antenna mounting apparatus according to the second aspect,    -   a further antenna mounting apparatus having:        -   a further first mount,        -   a further antenna mounting bracket attached to the further            first mount via a further rotational joint to allow azimuth            adjustment rotation about the first axis,        -   a further second mount attached to the first mount via a            further second rotational joint to allow azimuth adjustment            rotation about the second axis,    -   in which the antenna mounting apparatus and the further antenna        mounting apparatus are spaced apart in the direction of the        first and second axes.

Various example mounting apparatuses in accordance with the presentinvention will be provided with reference to the following figures:

FIG. 1 is a side view of a prior art cellular antenna base station;

FIG. 2 is a perspective, exploded view of a first antenna mount assemblyin accordance with the present invention;

FIG. 3 is a perspective view of the antenna mount assembly of FIG. 2 inan assembled condition;

FIG. 4 is a further exploded view of the antenna mount assembly of FIG.2 from a rear angle;

FIG. 5 is a side exploded view of the antenna mount assembly of FIG. 2;

FIG. 6a is a rear view of a part of the antenna mounting assembly ofFIG. 2;

FIG. 6b is a section view of the part of the antenna mounting assemblyshown in FIG. 6 a;

FIG. 6c is a rear view of the part of the antenna mounting assemblyshown in FIG. 6 a;

FIG. 7 is a close-up view of a part of the antenna mounting assembly ofFIG. 2;

FIG. 8 is a further close-up view of another part of the antennamounting assembly of FIG. 2;

FIG. 9a is a plan view of the antenna mounting assembly of FIG. 2 in afirst condition;

FIG. 9b is a plan view of the antenna mounting assembly of FIG. 2 in asecond condition;

FIG. 9c is a view of the antenna mounting assembly of FIG. 2 in a thirdcondition;

FIG. 10 is a detailed, exploded view of a part of a second antennamounting assembly in accordance with the present invention;

FIG. 11 is a further detailed, exploded view of the part of the antennamounting assembly of FIG. 10;

FIG. 12 is a detailed, exploded view of the part of the antenna mountingassembly of FIG. 10 with automated steering and locking;

FIG. 13 is a further detailed, exploded view of the part of the antennamounting assembly of FIG. 10 with automated steering and locking;

FIG. 14 is a detailed view of the part of the antenna mounting assemblyof FIG. 10 with manual steering and locking;

FIG. 15a is a side view of a third antenna mounting apparatus inaccordance with the present invention;

FIG. 15b is a side view of the antenna mounting apparatus of FIG. 15awith an antenna installed thereon;

FIG. 16a is a detail, perspective view of a part of the antenna mountingapparatus of FIG. 15 a;

FIG. 16b is a detail, perspective view of a further part of the antennamounting apparatus of FIG. 15 a;

FIG. 16c is an exploded view similar to FIG. 16 b;

FIG. 17 is a schematic of the movement range of the antenna mountingapparatus of FIG. 15 a;

FIG. 18a is a perspective view of a part of the antenna mountingapparatus of FIG. 15 a;

FIG. 18b is a side section view of the part of FIG. 18 a,

FIG. 19a is a detail, perspective underside view of the part of thefirst antenna mounting apparatus in an alternative, automatedconfiguration;

FIG. 19b is a perspective top view of the part of the antenna mountingapparatus as shown in FIG. 19 a;

FIG. 19c is a detail, side view of the part of the antenna mountingapparatus shown in FIGS. 19a and 19 b;

FIG. 20a is a perspective view of a part of the antenna mountingapparatus shown in FIGS. 16a to 16 c;

FIG. 20b is an exploded perspective view of the part of the antennamounting apparatus shown in FIG. 20 a;

FIG. 21a is a plan view of a first mounting arrangement for the antennamounting apparatus of FIG. 15 a;

FIG. 21b is a plan view of a second mounting arrangement for the antennamounting apparatus of FIG. 15 a;

FIG. 22a is a side view of a fourth antenna mounting apparatus inaccordance with the present invention;

FIG. 22b is a side view of the antenna mounting apparatus of FIG. 22awith an antenna installed thereon;

FIG. 23a is a detail, perspective view of a part of the antenna mountingapparatus of FIG. 22 a;

FIG. 23b is a detail, perspective view of a further part of the antennamounting apparatus of FIG. 22 a;

FIG. 24 is a schematic of the movement range of the antenna mountingapparatus of FIG. 22 a;

FIG. 25 is a detail, perspective view of a part of the antenna mountingapparatus as shown in FIG. 22a showing some additional parts.

FIG. 26 is a perspective view of a fifth antenna mounting apparatus inaccordance with the present invention;

FIGS. 27a and 27b are plan views of a sixth antenna mounting apparatusin accordance with the present invention;

FIGS. 28a and 28b are plan views of a seventh antenna mounting assemblyin accordance with the present invention;

FIGS. 29a and 29b are plan views of a eighth antenna mounting assemblyin accordance with the present invention;

FIG. 30 is a side view of a ninth antenna mounting assembly inaccordance with the present invention; and,

FIG. 31 is a side view of a tenth antenna mounting assembly inaccordance with the present invention.

Turning to FIGS. 2 to 9 c, there is shown an antenna support 102 towhich an antenna assembly 114 has been attached by an antenna mountingassembly 100 according to the present invention. The antenna mountingassembly 100 comprises a reference frame 104, a tilt bracket 106, ahinge 108, a first antenna mount 110 and a second antenna mount 112. Adirectional GPS (D-GPS) antenna arrangement 116 is also provided forinitial installation purposes, but does not form part of the assembly100 during normal (post-installation) use.

The antenna support 102 is a tubular member (akin to the support 3 ofFIG. 1) defining a mast axis M. The antenna support 102 is orientedvertically in use at a height sufficient to provide the requiredcoverage from the antenna assembly 114. In use, the mast support 102 isattached to a mast as described with reference to FIG. 1.

The reference frame 104 is attached to the antenna support 102 via thehinged tilt bracket 106 (equivalent to the prior art tilt bracket 4) andthe joint 108 (equivalent to the prior art joint 5). The tilt bracket106 and joint 108 are better seen in FIGS. 7 and 8 respectively.

The tilt bracket 106 comprises a first clamping member 118, and a secondclamping member 120 which are configured to receive the antenna support102 and are joined at either respective end by threaded rods 122, 124.The rods 122, 124 can be adjusted in order to bring the clamping members118, 120 closer together in order to clamp the antenna support 102therebetween. A downwardly depending link arm 126 is provided which ishinged to the first clamping member 118 via a rotational joint having ahorizontal axis of rotation H1, perpendicular to the mast axis M. At thefree end of the link member 126, a second link member 128 is attachedwhich depends upwardly from the first link member 126 and is attachedthereto via a rotational joint having a horizontal axis of rotation H2,parallel to H1. At the free end of the second link member 128 there isprovided an attachment plate 130 which is rotatably attached to thesecond link member 128 for rotation about a horizontal axis of rotationH3, parallel to H1 and H2. An extensible linkage is thereby created inwhich the horizontal distance between the first clamping member 118 andthe attachment plate 130 can be adjusted.

Turning to the joint 108, similarly there is provided a first clampingmember 132, a second clamping member 134 and a pair of threaded rods136, 138 respectively, which are configured to clamp the antenna support102 between the clamping members 132, 134. In the joint 108, anattachment plate 140 is connected directly to the first clamping member132 via a rotational joint with a horizontal axis of rotation H4. H4 isparallel to H1, H2 and H3.

The tilt bracket 106 and joint 108 are known in the art, and havetraditionally had an antenna directly attached thereto as described withreference to FIG. 1. In the prior art, azimuth adjustment of the antennais undertaken by loosening the clamps and manually rotating the antennaabout the support.

Turning to the reference frame 104, this is shown in more detail inFIGS. 6a to 6c . The reference frame 104 is an elongate, extrudedaluminium part of generally planar construction having a long axis E.The reference frame 104 has an antenna support attachment face 142 andantenna attachment face 144 on an opposite side thereof.

A cross section of the reference frame 104 is shown in FIG. 6b . Thecross section defines an reference frame plane P on which a planar bodypart 105 lies, from which various extruded features extend perpendicularthereto. The reference frame 104 is symmetrical about a plane ofsymmetry S which is perpendicular to the plane P.

At both free ends of the cross section (i.e. along the long edges of thereference frame 104), and extending from the antenna attachment face144, there is provided a generally c-shaped clamp 146, having a mouth148 and a partially circular cavity 150 for receiving and clamping amember as will be described below. The clamp 146 is cantilevered to thebody part 105 of the member 104 and is resilient.

Moving inwardly towards the plane of symmetry S, on the antenna supportattachment face 142, there is provided a bolt retaining channel 152comprising two side walls 154, 156 extending perpendicular from theplanar part 105 of the reference frame 104. Each of the side walls 154,156 is generally parallel and terminates in a respective end wall 158,160. A mouth 162 is provided between the end walls 158, 160. It will benoted that the distance between the side walls 156, 154, 156 is greaterthan the width of the mouth 162 so a bolt head can be captured andretained between the side walls 156, 154 without being pulled outthrough the mouth 162. Because the channel 152 runs along the length ofthe reference frame 104, bolts can be slid along it and tightened whererequired.

Moving inwardly towards the plane of symmetry S, on the antennaattachment face 144, there is provided a channel 164 of substantiallythe same construction as the channel 152, i.e., configured so as toreceive a bolt head. In the centre of the cross section, coincident withand either side of the plane of symmetry S, there are provided threeribs in the form of castellations 166, 168, 170 in the body 105 in orderto provide bending and torsional stiffness to the reference frame 104.

The first antenna mount 110 is shown in more detail in FIG. 7. The firstantenna mount 110 comprises a first body 172 which is generallyrectangular in plan having opposing attachment flanges 174, 176 definedat a first end. Each of the flanges 174, 176 is provided with attachmentmeans in the form of a pair of vertically spaced bolts 178. Each pair ofbolts 178 on the respective flange 174, 176. The body 172 comprises agenerally rectangular cut-out 180 to reduce its weight.

At an opposite ends of the body 172 to the flanges 174, 176, there isprovided a joint receiving formation 182 which is arranged to receive arotational joint 184 having an axis of rotation J1.

The rotational joint 184 is connected to a second member 186 of thefirst antenna mount 110. The second member 186 is also generallyrectangular in plan and by virtue of the joint 184 is configured torotate relative to the first member 172 about the joint axis J1. At theopposite end of the second member 186 to the joint 184, the secondmember 186 defines two oppositely extending flanges receiving bolts in asimilar manner to the first member 172. This can be seen in FIG. 7, andwill not be described in further detail here.

Turning to FIG. 8, the second antenna mount 112 is shown in detail. Thesecond antenna mount 112 comprises a first member 188 which is similarto the first member 172 of the first antenna mount 110. The first member188 also comprises flanges 190, 192 and extends to a rotational joint194. A second member 196 of the second antenna mount 112 is alsoprovided and is generally similar to the second member 186 of the firstantenna mount 110. Between the first and second members 188, 196, thereis provided a joint 194 which is driven in rotation by a steering andlocking unit 200.

The steering and locking unit 200 comprises an electric motor such thatthe rotational relative position of the first and second members 188,196 can be adjusted. The steering and locking unit 200 has an input 202comprising power for the electric motor and motor control signals from acontroller (not shown) and an output 202 which outputs the rotationalposition of the motor and/or joint 194 from an encoder therein. Thejoint 194 has a joint axis J2 aligned with the joint axis J1 of thefirst antenna mount 110.

The steering and locking unit 200 is also configured to selectively lockthe relative rotational position of the first and second members 188,196. This locking mechanism (an example of which will be describedbelow) is independent of the motor such that any movement from motorbacklash is eliminated.

The steering and locking unit 200 also comprises a rotary encoder suchthat the relative rotational position of the first and second members188, 196 can be accurately determined. Because the encoder is onlymeasuring relative position, it can be relatively inexpensive (tens ofEuros). In this instance, an optical encoder is used.

Turning back to FIG. 7, the antenna assembly 114 comprises an antenna206, the antenna being of a known construction, i.e., having areflector, a series of dipoles and a cover thereover. The antenna 206 isa directional antenna used for cellular communications. The antennareflector is attached to a connector 208 which is constructed from asheet metal material and extends the length of the antenna 206. Theantenna connector 208 is in turn attached to a backplate 210, bymechanical fasteners in the backplate channels.

The backplate 210 is substantially identical to the reference frame 104.The backplate 210 has an extruded profile having a cross section thesame as that shown in FIG. 6b for the reference frame 104. The antennaconnector 208 is attached to the side indicated 142 in FIG. 6 b.

The backplate 210 has the additional benefit that it further inhibitselectromagnetic “leakage” from the rear of the antenna 206 whichproviding attachment functionality.

Turning to the GPS antenna 116, this is a directional GPS (D-GPS)antenna having a first elongate member 212 oriented along a D-GPS axis Gand at each end of the member 212 there is provided a respective GPSantenna 214, 216 which extends in the direction perpendicular to theaxis G. The global position of the two GPS antennas 214, 216 can be usedto determine the global heading of the axis G of the D-GPS antenna 116.This type of antenna, although it can accurately determine the globalposition of a component it is attached to, is expensive (tens ofthousands of Euros) and as such is used during installation only, aswill be described below.

The antenna mounting assembly 100 is assembled as follows.

The two antenna mounts 110, 112 are assembled to the reference frame104. This is shown in more detail in FIG. 7 in which the first member172 is attached to the reference frame 104 by using the bolts 178. Theheads of the bolts 178 are inserted in direction I into the channels 164(see FIG. 6b ) of the reference frame 104 such that they are slidablymoveable in direction L1 as shown in FIG. 7. By tightening the bolts 178the end wall of the channels 164 can be used to clamp the first member172 in place. The second antenna mount 112 is attached to the referenceframe 104 in a similar manner. Due to the planar abutment of the antennamounts with the intermediate member, and the location of the bolts 178in the channels 164, the antenna mounts are installed at a fixedorientation to the reference frame 104. No other relative orientation ofthe components when attached is possible.

The antenna assembly 114 is attached to the second members 186, 196 ofthe first and second antenna mounts 110, 112 are attached to thebackplate 210 in a similar fashion, i.e., bolts through the respectiveflange of the second member 186 are clamped into place using thechannels defined in the backplate 210.

Because the reference frame 104 and backplate 210 are extruded, and inparticular because the bolt-receiving channels therein are elongate, theantenna mounting assemblies 110, 112 can be moved in directions L1 andL2 as required. This allows a variety of different antennas to be usedwith the present invention.

The invention is particularly well suited to retrofit to existing basestation locations, and provides the aforementioned advantages withoutsignificantly increasing CAPEX with expensive new antennas andequipment.

Starting from an existing installation similar to that shown in FIG. 1,in existing base stations the existing antenna 206 is mounted directlyto a tilt bracket 106 and joint 108. The tilt bracket 106 and joint 108are clamped to the antenna support 102 oriented with axis M vertical.

According to the invention, starting from this known base station, theantenna 206 is removed and fitted with the backplate 210 to form theantenna assembly 114. The antenna assembly 114 is then fitted to thefirst and second antenna mounts 110, 112 as described above.

The reference frame 104 of the assembly 100 is then fitted to the tiltbracket 106 and joint 108 with bolts having heads captured in theantenna support side of the reference frame (channels 152—see FIG. 6b ).

Once mounted, the DGPS antenna 116 is then temporarily attached to thereference frame 104. It will be noted that the axis G of the DGPSantenna is parallel to the plane P of the intermediate member 104(although this is not essential). As such, the plane P of theintermediate member 104 is aligned with the axis G.

The absolute orientation of the reference frame 104 is then determinedto a high degree of accuracy using the D-GPS antenna 116. Oncedetermined, the D-GPS antenna is removed (and reused) and the referenceframe 104 is not moved thereafter. It will be noted that because theantenna is adjustable relative to the reference frame 104, there is noneed to adjust the position of the reference frame 104 with the D-GPSunit installed. The technician needs only to determine the globalposition and orientation of the reference frame 104. This furtherreduces error.

It will be noted that the tilt of the antenna about a horizontal axis H4shown in FIG. 8 can be achieved by articulating the first and secondlink members 126, 128 in the tilt bracket 106. This type of articulationis performed manually when the antenna is set up and is generallydependent on the height at which the antenna is mounted. This step isperformed before the absolute position of the reference frame 104 ismeasured.

Turning to FIGS. 9a to 9c , the properties of the antenna mountingassembly 100 are shown in plan. Turning to FIG. 9a , the antennaassembly 114 is shown with the antenna having a primary radiationdirection R perpendicular to the intermediate member 104 (which isaligned with the D-GPS axis G, shown for guidance only).

Because the system controller knows (i) the position and orientation inthe global sense of the reference frame 104, and (ii) the orientation ofthe antenna assembly 114 relative to the intermediate member 104 byvirtue of the rotary encoder provided within the steering and lockingunit 200, the global orientation of the antenna 114 can be determined.The angle α between the axis G and the general direction of radiation Rof the antenna 114 in FIG. 9a is 90 degrees. Turning to FIG. 9b , if thesteering and locking unit 200 is used to rotate the antenna arrangement114 by, for example, 45 degrees, it is known from the encoder that theangle α between G and R is now 45 degrees and this can be combined withthe known absolute heading of the reference frame 104 to determine theabsolute direction of radiation R. This is also true for FIG. 9c inwhich angle α is 135 degrees.

A joint 2194, an automated steering and locking assembly 2200, and amanual steering and locking assembly suitable for use with the antennamounting assembly 100, are shown in FIGS. 10 to 13. The joint 2194differs in minor constructional details to the joint 194, but itsfunction is the same.

Referring to FIGS. 10 and 11, the joint 2194 is shown. FIG. 10 shows thejoint 2194 inverted. The joint 2194 comprises an interface plate 2000which is generally circular and has an upstanding rim 2002 at itsperiphery. The plate 2000 defines an input drive bore 2004, a stop pinbore 2006 and a data connector 2008 in its lower surface.

Opposite the interface plate 2000, and engageable therewith there isprovided a cover plate 2010 which is configured to assemble to theinterface plate 2000 and form an IP67 level (International ProtectionRating) seal therewith around an inner volume.

The cover plate 2010 defines an output drive bore 2012 in its centre,concentric with the input drive bore 2004 of the interface plate 2000.

Within the joint 2194 there is provided a drive shaft 2014 one end ofwhich is accessible from the drive bore 2012 of the cover plate forattachment of e.g. the second member 196 of the assembly 100. The other(lower) end of the drive shaft 2014 is accessible from the input drivebore 2004.

A locking plate 2016 is provided. The locking plate 2016 is a 180 degreecircle segment having a geometric centre bore 2018 and a series oflocking bores 2020 positioned at a set radius R from the centre bore2018 and spanning 180 degrees. The locking plate is attached to thedrive shaft 2014 at the centre bore 2018 such that it can rotatetherewith about the joint axis J2.

An optical encoder 2022 is provided to receive the drive shaft 2014 andmeasure relative rotation thereof. The optical encoder 2022 is attachedto the interface plate 2000, but receives the drive shaft to measure itsrotation. The optical encoder 2022 is connected to provide an outputsignal to the connector 2008 to deliver data representative of thedegree of rotation of the shaft 2014 relative to the housing defined bythe interface plate 2000 and the cover plate 2010.

The joint 2194 also comprises tilt and roll sensors (which arerelatively inexpensive), and data regarding the tilt and roll angles ofthe reference frame (to which the joint 2194 is attached) are also fedto the connector 2008. Therefore the connector 2008 is a source of tilt,roll and relative heading data.

A pair of adjacent bearings 2024, 2026 are provided to receive the driveshaft 2014 and support it in use.

Turning to FIGS. 12 and 13, a steering and locking assembly 2200 similarto the steering and locking assembly 200 is shown in detail, assembledwith the joint 2194.

The steering and locking assembly 2200 comprises a housing 2028 having acover 2030, which housing is IP67 sealed. The assembly 200 contains anelectric motor 2032, a step down gearbox 2034 and a separate stop pinactuator 2036 comprising a solenoid. The gearbox has an output shaft2038 which can be driven in rotation by the motor 2032, and the stop pinactuator is connected to a linearly actuable stop pin 2040 at a distanceR to the shaft 2038. Both the shaft 2038 and the stop pin 2040 projectfrom the housing 2028.

An electrical connector 2042 is provided between the shaft 2038 and thestop pin 2040 on the outside of the housing 2028.

The interface plate 2000 of the joint 2194 acts as a plug and playinterface for either an automated (FIGS. 12 to 13) or manual (FIG. 14)actuation system. The interface plate presents a steering input, alocking input and a data output from the encoder.

As shown in FIG. 12, the steering and locking assembly 2200 can beassembled to the interface plate 2000 so that the output shaft 2038 candrive the drive shaft 2014, and the stop pin 2040 can selectively engagethe locking bores 2020 on the locking plate 2016. The electricalconnector 2042 interfaces with the connector 2008 on the interface plateto retrieve data from the optical encoder 2022. The steering and lockingassembly 2200 and the interface plate 2000 are IP67 sealed by means ofseal 2023 which surrounds the three interfaces.

The assembly of the joint 2194 and steering and locking assembly 200therefore provides an accurate relative positioning system, in which thedrive shaft 2014 (and therefore the second member 196) can be steered(resulting in azimuth adjustment of the antenna) whilst accuratelymeasuring relative rotational position and providing locking when in thedesired position, to eliminate any error or movement from motor orgearbox backlash.

It will be noted that the optical encoder 2022 takes a reading directlyfrom the shaft 2014—i.e. directly from the antenna. In other words theencoder is on the antenna side of the gearbox 2034. The connectionbetween the antenna and the encoder 2022 is therefore direct andungeared. Advantageously this means that the encoder measures the trueposition of the antenna without any problematic error or backlash whichcan be introduced if the encoder was positioned e.g. on the oppositeside of the gearbox 2034 to the antenna. Therefore this system offers anadvantage over e.g. systems using a position sensor integral with themotor 2032.

The data provided by the connector 2008 (specifically tilt, roll andrelative heading compared to the reference frame) can be used tocalculate the global orientation of the antenna using the absoluteposition of the reference frame determined during set up. This globalorientation can be used to steer the antenna to the desired position asdemanded by the network operator. We refer to the applicant's earlierapplication WO2013/011002 for details on this alignment method.

Instead of the automated steering and locking assembly 2200, analternative manual steering and locking assembly 2500 is shown in FIG.14, assembled with the joint 2194.

The manual assembly 2500 comprises a casing 2502 having a through borefor a steering shaft 2504 and a resilient locking pin 2506 associatedtherewith. The assembly 2500 also comprises an electrical data connector(not visible) arranged to connect to the electrical connector 2008 toreceive position data from the optical encoder 2022 and display it on adisplay panel 2508.

In use, the assembly 2500 is attached to the interface plate 2000 asshown in FIG. 14 such that a manual tool 2510 (e.g. a T-bar) can beinserted into the through bore for a steering shaft 2504 to access thedrive shaft 2014 and thereby steer the antenna.

During such rotation, the locking pin 2506 must be pulled to disengage aprojecting pin (similar to the pin 2040) from the locking plate 2016.Once released, the pin 2506 resiles under the action of a spring (notshown) towards the plate 2016 and will engage with the relevant bore2020 to lock the drive shaft 2014 in place.

During rotation of the tool 2510 (an hence the antenna) the displaypanel 2508 will accurately read the position of the antenna based on theknown absolute position of the reference frame 104 (determined andelectronically stored during setup) and the relative rotation of theantenna with respect to the reference frame as determined by the opticalencoder 2022.

The manual and automated systems can be freely interchanged—for examplean antenna installation may be initially provided with the manualsystem, and later upgraded to the automated system when more frequentadjustment is required.

Turning to FIGS. 15a to 20b , there is provided a simpler antennamounting apparatus 3010. The apparatus comprises an upper mount assembly3012, a lower mount assembly 3014 and a stability bar 3016 extendingtherebetween. As shown in FIG. 15b , an antenna 3018 can be attached toboth the upper and lower mount assemblies 3012, 3014 (as will bedescribed below) in order to position it for use in a cellularcommunications network.

Turning to FIG. 16a , the upper mount assembly 3012 is shown in moredetail. The upper mount assembly 3012 comprises a mount 3020 and anantenna bracket 3032.

The mount 3020 has a flat rectangular body 3022. At a first end of thebody 3022 oppositely extending attachment flanges 3024, 3026 areprovided such that the mount 3020 is “T” shaped in plan view. Each ofthe flanges 3024, 3026 defines an open horizontal bore through thevertical faces thereof for attachment to a mounting arrangement viamechanical fasteners 3025, 3027. Each of the through bores is orientedin a direction parallel to a main axis of the body 3022. The body 3022also defines a square blind bore (not shown) on its underside proximatethe flanges 3024, 3026. At the opposite end of the body 3022 to theflanges 3024, 3026, a bearing mount region 3028 is provided whichdefines a vertically oriented joint receiving formation 3030.

The antenna bracket 3032 is generally shaped as an inverted “L” incross-section. The bracket 3032 comprises a vertical antenna attachmentflange 34 forming the vertical leg of the inverted “L” defining severalslots 3036 for the passage of mechanical fasteners 3038 to attach theantenna 3018 to the flange 3032. A bearing mount flange 3040 is providedextending horizontally from the upper edge of the antenna attachmentflange 3034 to form the horizontal leg of the inverted “L”. The bearingmount flange 3040 is generally semicircular in shape. The bearing mountflange 3040 also defines a vertically oriented joint receiving formation(not visible).

To assemble the upper mount assembly 3012, a rotational joint 3042comprising a bearing is simultaneously installed in the joint receivingformation 3030 of the bearing mount region 3028 and the joint receivingformation of the bearing mount flange. The rotational joint bearing isof known type, and as such will not be described in detail here. Itprovides a rotational degree of freedom for rotation of the bracket 3032relative to the mount 3020 about an azimuth steering axis X.

The lower mount assembly 3014 is shown in more detail in FIG. 16b (withthe antenna 3018 detached) and 16 c (with the antenna 3018 attached).Like the upper mount assembly 3012, the lower mount assembly 3014comprises a mount 3044 and an antenna bracket 3060.

The mount 3044 comprises a stepped body 3046 having a first region 3047stepping down in thickness to a second region 3049. At the end of thefirst region 3047 opposite the second region 3049 there are provided twoflanges 3048, 3050 extending oppositely to form a T-shape in plan view.The flanges 3048, 3050 comprise horizontal through bores for theattachment of mechanical fasteners 3045, 3051 for mounting the assemblyto an appropriate mounting arrangement.

The first region 3047 of the stepped body 3046 defines a blindrectangular bore 3052 on it upper surface. A threaded grub screw hole3054 extends from an accessible outer side of the stepped body 46 and isin communication with the rectangular bore 3052.

A vertical pin receiving through bore 3056 is provided in the firstregion 3047 of the stepped body 3046 proximate the rectangular bore3052. The pin receiving bore is provided as close as possible to, but onthe second region 3049 side of, the rectangular bore 3052.

The second region 3049 comprises a bearing plate 3058. The bearing plate3058 defines a vertically oriented joint receiving formation (notvisible).

The antenna bracket 3060 comprises a vertical attachment flange 3062, abearing support 3064 and a locking plate 3066.

The attachment flange 3062 defines a number of bores 3065, suitable forreceiving mechanical fasteners 3066 in order to secure the antenna 3018thereto. The bearing support 3064 extends horizontally (i.e.perpendicularly) from the flange 3062 and comprises a pair of offsetplates.

The locking plate 3066 comprises a bearing plate 3067 and a fan plate3070 integral therewith. The bearing plate 3067 is generally square anddefines a central square through bore 3069. The fan plate 3070 extendsfrom the bearing plate 3067 an describes a 130 degree circle segment,with its centre of curvature at the centre of the through bore 3069. Thefan plate 3070 has an outer edge 3072 describing a 130 degree circlesegment, proximate which an arcuate row of pin receiving through bores3074 are provided at a common radius. Turning to FIG. 17, furthergeometric detail of the locking plate 3070 is shown. As will be seen,each of the bores 3074 are positioned at a common radius R and 5 degreesapart ranging from −60 to +60 degrees. Therefore, the total range ofazimuth steering is 120 degrees.

The flange 3062 and the bearing support 3064 are integral. The lockingplate 3066 is attached to the bearing support 3064 by means ofmechanical fasteners 3068. The flange 3062, bearing support 3064 andlocking plate 3066 are all perpendicular.

A rotational joint 3076 comprising a roller bearing is provided anddisposed to permit rotation between the antenna mounting bracket 3060and the mount 3044 about the azimuth steering axis X. The rotationalbearing assembly 3076 is mounted to the bearing plate 3058 in the jointreceiving formation such that it projects upwards between the verticalplates of the bearing support 3064 (see FIG. 16c ).

A pivot pin 3077 is provided, having a shaft 3079 with a square profile3081 near its head. The pivot pin 3077 is fed through the square throughbore 3069 and rotatably engages the bearing assembly 3076. The pivot pin3077 also projects to the other (lower) side of the joint 3076 and thebearing plate 3058 (see FIG. 19a ). The mating between the squareprofile 3081 and through bore 3069 locks the antenna bracket 3060 andpin 3077 together such that whilst both can rotate via the joint 3076relative to the mount 3044.

The projection of the pivot pin allows for easy retrofit of the anactuator should the operator want to move to an automated system.

It will be noted that the distance from (i) the centre of rotation ofthe joint receiving formation in the bearing plate 3058 and (ii) the pinreceiving bore 3056 is the same as the distance from (iii) the centre ofthe square through bore 3069 to (iv) each of the plurality of bores 74.Therefore as the joint 76 is rotated about the axis ‘X’, then the pinreceiving bore 3056 will sequentially align with each of the pluralityof bores 3074.

It will also be noted that the locking plate 3060 rests on the body 3046of the mount 3066 and slides over it.

The stability bar 3016 is generally square in cross-section and isconfigured to fit into the square bore on the underside of the mount3020 as well as the square bore on the top side of the mount 3060. Aswell as maintaining the distance between the mounts, the bar alsoresists any torsional forces generated therebetween by movement of theantenna by actuation, or e.g. wind loading. The stability bar 3016 issecured in position with the use of radial grub screws (see bore 3054).It will be noted that the stability bar is replaceable to allowdifferent sizes of antenna to be accommodated in the apparatus 3010.

The invention may be provided in a manual, or a remotely actuatedversion.

In the manual configuration of the present invention, a retractable pinassembly 1000 is provided, as shown in detail in FIGS. 18a and 18b . Thepin assembly 1000 comprises a hollow shaft 1002 having a through bore1004 and an annular channel 1006 defined in an inner sidewall thereof. Apin member 1008 is provided having a head 1010 with a flange 1012. Thehead 1010 extends into a shaft 1014 having a free end 1016. The shaft1014 comprises an annular flange 1018 which slides within the annularchannel 1016. A compression spring 1020 is positioned within the channel1006 and may be compressed by the flange 1018 such that the shaft 1014resiles to an extended position from the shaft 1014.

In use, an operator can access the antenna, pull the head 1010 by theflange 1012 to retract the pin member 1008 and rotate the antenna asrequired. When the pin member 1008 is released the spring will urge thepin member 1008 into the extended position shown in FIG. 18b and lockthe antenna in position. It will be noted that if the relevant bores arenot properly aligned, a small movement of the antenna in eitherdirection (e.g. under wind loading) will result in alignment and the pinmember will always “snap” into position, inhibiting further movement ofthe antenna. Therefore the system has a failsafe condition should theoperator forget to ensure that the locking mechanism has engaged.

Turning to FIGS. 19a to 19c , a remotely actuated version of the presentinvention is shown. A drive assembly 3100 (described in more detailbelow) is provided having an output shaft 3102 projecting from anattachment plate 3104. As shown in FIG. 19a , the attachment plate 3104is secured to the underside of the second region 3049 of the steppedbody 3046 of the bearing plate 3058. Fasteners 3106 are provided forthis purpose.

As described above, the pin 3077 projects below the bearing plate 3058and is engageable by the output shaft 3102 to drive it in rotation.Known rotary couplings may be used for this purpose, such as a splinedcoupling, or shaft with a flat. It will be noted that once the driveassembly 3100 has been attached, actuation thereof will drive the pin3077 which, by virtue of its engagement with the locking plate 3066 ashereinbefore described, with act to rotate the antenna 3018 about theazimuth rotation axis X. The upper mount assembly 3012 is free inrotation.

The drive assembly 3100 is shown in more detail in FIGS. 20a and 20b .The drive assembly 3100 comprises a housing 3116 defining the attachmentplate 3104 on a top surface thereof. The housing 3116 has a removablebase 3118.

An electric motor 3120 is provided comprising a gearbox 3121 whichdrives the output shaft 3102. The shaft 3102 projects from theattachment plate 3104 when the motor is installed in the housing 3116.The electric motor 3120 further comprises an encoder 3122 which measuresthe rotation of the motor 3120, and therefore the rotation of the gearedoutput shaft 3102 can be calculated. A local control unit 3124 isprovided, which as well as controlling the motor 3120, can step themotor by desired increments from an input demand via a connector 3126.The local control unit 3124 receives a request from a remote controlstation, e.g. to move to +30 degrees azimuth, and activates the motor3120 to move the antenna 3018. When the encoder 3122 reports that themotor has moved by the desired amount (taking account of the gearing),the local control unit stops the motor 3120. Feedback can be provided tothe remote control station via a connector 3128.

The local control unit 3124 further comprises a stop output connector3130.

Turning back to FIGS. 19a and 19b , a stop assembly 3108 is alsoprovided. The stop assembly 3108 comprises a linear output pin 3110,which can be moved in an axial sense. The assembly 3108 is fastened tothe underside of the first region 3047, as shown in FIG. 19a bymechanical fasteners 3112. The linear actuator 3110 is engageable with astop pin 3114, which can be driven in a vertical manner from a retractedposition in which engages only with pin receiving bore 3056 to anextended position in which it engages with both the pin receiving bore3056 and the one of the plurality of bores 3074 with which it isaligned.

When the antenna is static, the linear output pin is extended, such thatthe stop pin 3114 engages and locks the mount 3044 to the antennabracket 3060, effectively preventing the joint 3076 from articulating.

When the local control unit 3124 receives a signal to move the antenna3018, it commands the stop assembly 3108 to retract the pin 3110 andtherefore the pin 3114 to the retracted position. The bracket 3060 canthen rotate relative to the mount 3044. The local control unit 3124 thenactuates the antenna using the motor 3120 as described above until theencoder report the desired position has been reached. Once the desiredposition has been reached, the stop assembly 3108 is commanded to pushthe pin 3114 into the extended position, thereby locking the antenna inplace. The local control unit is configured to only step by multiples of5 degree segments. It will be noted that whilst the pin 3114 isactuated, the motor 3120 holds the antenna in place, to prevent anymisalignment from external loading (e.g. wind). Only when the pin 3114is engaged does the motor 3120 become inactive.

Because the locking plate 3070 is in contact with the mount 3044, thepin 3114 is placed in shear loading only, and not in bending (as wouldoccur with a gap therebetween). This makes the pin 3114 structurallymore effective.

Any subsequent wind loading can be resisted by the pin 3114, rather thanthe more delicate and expensive drive assembly 3100. The drive assembly3100 to be designed only to be able to drive the antenna in rotationwhilst the majority of the reaction load caused by back driving (such aswind) can be resisted by the lock 3108.

Turning to FIGS. 21a and 21b , various mounting arrangements are shown.For example, in FIG. 21a , the bores in the flanges 3024, 3026 have beenused to attach the antenna mounting bracket to a wall 3080. Turning toFIG. 21b , the same bores 3024, 3026 have been used to attach theantenna mounting apparatus to a pole 3082 using a clamp 3084.

Turning to FIGS. 22a to 25, a further embodiment of the presentinvention is shown. Like reference numerals numbered 200 greater will beused for components which are similar to those in the mounting apparatus3010.

A mounting apparatus 3210 is shown in FIGS. 22a to 25. Like mountingapparatus 3010, mounting apparatus 3210 comprises an upper mountassembly 3212, a lower mount assembly 3214 and a stability bar 3216,extending therebetween. An antenna 3218 can be positioned on both theupper and lower mount assemblies 3212, 3214 to be actuated and steeredin an azimuth direction.

Turning to FIG. 23a , the upper mount assembly 3212 is shown in moredetail. The upper mount assembly 3212 comprises a mount 3220, anintermediate member 3300 and an antenna bracket 3232.

The mount 3220 is somewhat similar to the mount 3020 of the apparatus3010, however, the flat rectangular body 3222 of the mount 3220 isshorter. Flanges 3224, 3226 are still provided, as is a verticallyoriented joint receiving formation 3230.

An intermediate member 3300 is provided which comprises an elongate,flat body 3302, having a first joint receiving formation (not shown) ata first end, and a second joint receiving formation 3304 defined at asecond end.

The antenna bracket 3232 is identical to the antenna bracket 3032 of theapparatus 3010.

In order to assemble the upper mount assembly 3213, the intermediatemember 3300 is attached via a first rotational joint 3306 for rotationabout a first azimuth steering axis X′ to the mount 3220. The antennabracket 3232 is attached to the intermediate member 3300 via a furtherrotational joint 3308 for rotation about a second azimuth steering axisX″.

Turning to FIG. 23b , the lower mount assembly 3214 is shown in moredetail. The lower mount assembly 3214 also comprises a mount 3244, anintermediate member 3310 and an antenna bracket 3260.

As with the upper mount assembly 3212, in the lower mount assembly 3214,the mount 3244 is substantially similar to the mount 3044 of theapparatus 3010, however, the body 3246 is somewhat shorter, having ajoint receiving formation (not visible). The mount 3244 defines a pairof horizontal flanges 3324, 3326 extending either side of the jointreceiving formation. The first flange 3324 comprises a verticallyoriented pin receiving bore (not visible). The second flange 3326defines an arcuate slot 3328 (see FIG. 24). The arcuate slot 3328 has ageometric centre aligned with the joint receiving formation.

The intermediate member 3310 comprises an elongate body 3312 whichdefines on its upper surface a square bore 3314 to receive the stabilitymember 3216. At the first end of the body 3312 there is provided a mountjoint receiving formation 3316. At either side of the mount jointreceiving formation 3316 there are provided horizontal flanges 3318,3320. The first horizontal flange 3318, at its outer periphery, definesthree pin bores 3322 which are located at an equal radius about thecentre of the mount joint receiving formation 3316. The secondhorizontal flange 3320 comprises a downwardly depending stop pin 3330. Abracket joint receiving formation (not visible) is provided at a secondend of the body 3312.

The antenna bracket 3260 is identical to the bracket 3060 of apparatus3010.

The intermediate member 3310 is pivotably attached to the mount 3244 viaa rotational joint (not visible) fitted into the joint receivingformation in the mount 3244 and the mount joint receiving formation 3316in the intermediate member 3310. Rotation occurs about the first azimuthsteering axis X′. The stop pin 3330 slides in the arcuate slot 3328, andas well as guiding the relative motion of the two components preventsover actuation which may cause damage to the antenna 3218.

The bracket 3260 is attached to the intermediate member via a rotationaljoint (not shown) between the bracket joint receiving formation of theintermediate member and the joint receiving formation of the bracket.Rotation occurs about second azimuth steering axis X″. The rotation canbe powered and locked in the same way as apparatus 10 using anappropriate drive apparatus 3500 and stop apparatus 3502 as shown inFIG. 25.

Turning to FIG. 24, as can be show there are two parallel articulationaxes, X′ and X″ of the apparatus 3210. The three bores 3322 provided onthe flange 3318 are spaced 10 degrees apart such that the intermediatemember 3310 can be pivoted about the first azimuth steering axis X′.This provides an even greater range of motion for the antenna 3018 as itcan now be steered by +/−60 degrees about axis X″ and, in addition, afurther +/−10 degrees about axis X′. In particular, this gives theantenna 3018 the ability to face further left or right depending on therequirements of the user.

Turning to FIG. 26, an assembly of an antenna mount 502, a first antennaassembly 514 and a second antenna assembly 1014 are shown, the first andsecond antenna assemblies 514, 1014 attached to the antenna mount 502 byan antenna mounting assembly 500 according to the present invention.

The antenna mount 502 has a mast axis M and is the same as the antennamount 102. The first and second antenna assemblies 514, 714 are each thesame as the antenna assembly 114.

The antenna mounting assembly 500 comprises:

-   -   (i) a common reference frame 504, substantially the same as the        reference frame 104, but longer in a long axis E;    -   (ii) a tilt bracket 506;    -   (iii) a pivot 508;    -   (iv) a first antenna mount 510 the same as the first antenna        mount 110;    -   (v) a second antenna mount 512 the same as the second antenna        mount 112;    -   (vi) a third antenna mount 1010 the same as the first antenna        mount 110; and,    -   (vii) a fourth antenna mount 1012 the same as the second antenna        mount 112.

It will be noted that the antenna assemblies 514, 1014 are connected tothe same reference frame 504, and as such they share a datumorientation, as the antenna mounts 510, 512, 1010, 1012 can only beattached to the reference frame in a predetermined orientation. As such,using the rotary encoders sensors embedded in the joints of the secondand fourth antenna mounts 510, 1010, the antenna assemblies 514, 1014can be accurately aligned for MIMO applications. Advantageously, theextruded nature of the reference frame 504 allows the antenna assembliesto be moved in direction E to set the ideal spacing between theirrespective top dipoles, which for MIMO applications is greater than orequal to 10 wavelengths of the radiation emitted/received. For examplefor a 700 MHz signal this is 4.29 m, or for 1800 MHz it is 1.67 m.Generally, cellular communication is in the 700 to 3000 MHz order ofmagnitude.

Turning to FIGS. 27a and 27b , an assembly of an antenna support 1502and a first antenna assembly 1514 is shown, attached by an antennamounting assembly 1500 according to the present invention.

The antenna assembly comprises an antenna having a breadth B and a depthD.

The antenna mounting assembly 1500 comprises a reference frame 1504attached to the antenna support 1502 by a tilt bracket 1506. Thearrangement is similar to the assembly 1500.

The distance X between the reference frame 1504 and the axis of rotationof the antenna assembly 1514 is such that due to the breadth B of theantenna assembly 1514 the maximum rotation angle γ is 30 degrees.

By altering the distance X as shown in FIGS. 28a, 28b, 29a, 29b , theangle γ can be increased to 45 and 90 degrees respectively. γ=90 degreeswhen X=B/2.

Turning to FIGS. 30 and 31, two different assemblies 4000 and 4500 areshown. The assembly 4000 comprises a first and second spaced apart mount4002, 4004 with a common axis of azimuth rotation 4006. The assembly4500 comprises a first and second spaced apart mount 4502, 4504 with acommon axis of azimuth rotation 4506.

The assembly 4000 comprises an antenna assembly 4008, and the assembly4500 comprises an antenna assembly 4508. In the assembly 4000, the axis4006 is coincident with the antenna assembly 4008. This makes for acompact assembly in the horizontal direction, but at the expense of along vertical arrangement, By contrast, in the assembly 4500, the axis4506 is midway between the relevant antenna mount and the antennaassembly 4508, which makes the system larger in the horizontal sense,but more compact in the vertical sense (such that a much larger antennacan fit in to the same space envelope per FIG. 31).

Variations fall within the scope of the present invention.

Actuation and stopping about the steering axis X′ may be automated inaddition to the steering about axis X″. This may involve a further motorand stop apparatus driven by the local control unit.

Various embodiments have been described herein, but the skilledaddressee will understand that the various components, systems andmethods are interchangeable between embodiments.

The invention claimed is:
 1. A method of modifying an existing cellularantenna base station, comprising the steps of: providing an existingcellular antenna base station comprising a mast; providing a referenceframe; providing a global orientation and position measurement device;measuring a global orientation of the reference frame about a first axisusing the global orientation and position measurement device; removingthe global orientation and position measurement device, leaving thereference frame in-situ; providing an antenna mounting assembly havingan antenna bracket, the antenna mounting assembly comprising arotational joint and a first locking mechanism, the first lockingmechanism comprising: a plate connected to one of the mast and theantenna mounting bracket, the plate comprising a plurality ofspaced-apart openings, and a locking pin connected to the other of themast and the antenna mounting bracket, the locking pin configured tomove between an unlocked condition and a locked condition in which thelocking pin engages one of the plurality of openings in the plate toprevent movement of the rotational joint, and wherein the antennamounting assembly is configured to allow movement and locking of theantenna bracket in a plurality of predetermined angular positions aboutthe first axis with respect to the mast; and, attaching an antenna tothe antenna bracket.
 2. The method of claim 1, in which the existingcellular antenna base station comprises a tilt bracket attached to themast, and the step of providing the reference frame comprises the stepof attaching the reference frame to the tilt bracket.
 3. The method ofclaim 1, in which the existing cellular antenna base station comprisesthe antenna attached to the mast.
 4. A method according to claim 1,comprising the steps of: providing a sensor on the antenna mountingassembly, the sensor configured to measure the position of the antennabracket relative to the mast providing an azimuth steering assemblycomprising the rotational joint; steering the antenna using the azimuthsteering assembly; determining the absolute heading of the antenna usingthe measured position of the reference frame combined with data providedby the sensor.
 5. A method according to claim 1, comprising the stepsof: providing a further antenna; attaching the further antenna to thereference frame.
 6. The method of modifying an existing cellular antennabase station according to claim 1, in which: the antenna is adirectional cellular communications antenna; and the method furthercomprises the steps of: providing a further antenna mounting assembly,spaced apart from the antenna mounting assembly, the further antennamounting assembly having a further antenna bracket, the further antennamounting assembly comprising a further rotational joint and a furtherfirst locking mechanism comprising a further plate and a further lockingpin engageable with the further plate to prevent movement of the furtherrotational joint; wherein the rotational joint and the furtherrotational joint are aligned on a substantially vertical axis in use toprovide azimuth steering of the directional cellular communicationsantenna.
 7. The method of claim 2, in which the existing cellularantenna base station comprises an antenna mount attached to the tiltbracket, and the step of providing the reference frame comprises thestep of attaching the reference frame to the antenna mount.
 8. Anantenna mounting apparatus comprising: a first mount, an antennamounting bracket attached to the first mount via a first rotationaljoint to allow rotation about a first, azimuth steering, axis in use;the first rotational joint comprising: a first locking mechanismarranged to lock the first rotational joint against rotation, the firstlocking mechanism comprising: a plate connected to one of the firstmount and antenna mounting bracket, the plate comprising a plurality ofspaced-apart openings; and a locking pin connected to the other of thefirst mount and antenna mounting bracket, in which the locking pin isarranged to move between an unlocked condition and a locked condition inwhich it engages one of the plurality of openings in the plate toprevent movement of the rotational joint.
 9. An antenna mountingapparatus according to claim 8, in which the plurality of spaced-apartopenings are circumferentially spaced around the first, azimuthsteering, axis at a first radius.
 10. An antenna mounting apparatusaccording to claim 8, in which the locking pin is linearly actuable. 11.An antenna mounting apparatus according to claim 8, comprising a rotarysensor arranged to determine the articulation of the first rotationaljoint.
 12. The antenna mounting apparatus according to claim 8, whereinthe locking pin is actuated by an electric actuator.
 13. The antennamounting apparatus according to claim 8, further comprising an electricsteering actuator arranged to rotate the antenna mounting bracketrelative to the first mount.
 14. An antenna mounting apparatus accordingto claim 10, in which the locking pin is resiliently biased to a lockedcondition.
 15. An antenna mounting apparatus according to claim 11,wherein the first rotational joint comprises an interface platedefining: a drive interface for articulating the joint, a lockinginterface for selectively locking the joint using the first lockingmechanism, and a rotary sensor interface arranged to provide an outputreading from the rotary sensor.
 16. An antenna mounting apparatusaccording to claim 15, in which each interface of the interface platefaces in a common direction.
 17. An antenna mounting apparatus accordingto claim 15 in which the interface plate defines an actuator mountingformation for attachment of an actuator housing to engage an actuatoroutput shaft with the drive interface in use.
 18. An antenna mountingapparatus according to claim 15, in which the first rotational jointcomprises a sealed housing containing the first locking mechanism andthe rotary sensor.
 19. An antenna mounting apparatus according to claim16, in which the common direction is towards the ground in use.
 20. Anantenna mounting apparatus according to claim 18, in which the sealedhousing is sealed to an IP rating, preferably an IP rating of at leastIP67.